This invention arose in the field of endoscopic surgical devices but also pertains to the field of fiber optics.
There is great incentive to make endoscopes smaller. Smaller endoscopes make endoscopic surgeries less invasive and healing times shorter. If the endoscopes are small enough, the entire procedure can be carried out in a doctor""s office, without general anesthetic, on an outpatient basis, resulting in a substantial cost savings. Today, most endoscopes in use are rigid endoscopes, comprising chains of lenses. An introducer at least 6 millimeters in diameter must be inserted in the patient""s body to conduct surgery with the smallest of these. Applicants are working to develop flexible, serviceable, and affordable fiber optic endoscopes by means of which surgeries may be conducted through an introducer 2 millimeters or less in diameter.
In a typical endoscopic surgery, the introducer is a cannula with a trocar through its center, which is inserted into the patient""s joint. The trocar is then withdrawn and the endoscope inserted. The endoscope is connected to a camera through an adapter that clips on to the base of the endoscope. A wire from the camera carries the image to a video processor.
The person conducting the surgery holds the camera while manipulating the endoscope. Although orthopedic surgeons have become used to holding cameras while conducting these surgeries, relieving them of this burden could only enhance their ability to conduct them.
An important issue in conducting surgeries of this type is maintaining sterile conditions. For this purpose, a sterile field is created. A sterile field is an area around the point of incision that is prepared before a surgical procedure and maintained during the procedure. The preparation and maintenance of a sterile field is described in Atkinson and Fortunato, Berry and Kohn""s Operating Room Technique (8th ed. 1996). All items within the sterile field must be sterilized. In prior art endoscopic surgeries, the camera, wire, and adapter are within the sterile field. Federal regulations and good practice therefore require these parts to be sterilized between uses. This is inconvenient, time consuming, and reduces the availability of the apparatus for use in other surgeries. Furthermore, the sterilization procedure can damage the electronic components.
In one respect, the present invention comprises a method of conducting endoscopic surgery in which the camera is outside the sterile field. According to this method, the camera is placed outside the sterile field and the image is transmitted to the camera by a fiber optic cable. Preferably, the apparatus for conducting the surgery is organized so that the person conducting the surgery does not have to hold the camera while manipulating the endoscope.
The inventors observed that use of a single long fiber optic cable to carry the image outside the sterile field would makes this procedure expensive. The initial cost of such a cable would be high and even with care it is inevitable that it would be damaged during use. The cable would probably not last through ten surgeries.
To ameliorate this expense, the inventors developed a segmented fiber optic cable. By a segmented fiber optic cable, applicants mean an image transmitting fiber optic cable formed by the union of two or more separate fiber optic cables. Applicants observed that a short segment of the cable nearest the patient is the portion most likely to be damaged during use. In a segmented fiber optic cable, this portion (called the xe2x80x9cdisposable cable portionxe2x80x9d, although it may be used several times) may be replaced while the longer portion of the cable (the xe2x80x9creusable cable portionxe2x80x9d) continues to be reused. The reusable cable portion can also be armored. While such armoring on the disposable cable portion might interfere with the operation of the endoscope and would, in any case, excessively increase the diameter of the introducer, armoring on the reusable cable portion presents no disadvantages. An armored reusable cable portion is expected to withstand upwards of a hundred surgeries.
In developing a segmented fiber optic cable, the inventors were faced with the problem of connecting the segments in a way that would preserve the image quality required for surgical procedures. Fiber optic cables comprise bundles of optical fibers. Thousands of fibers are required to form a satisfactory image. Image preserving connections between such bundles of image transmitting fibers appear to have been unknown prior to applicant""s invention. By an image preserving connection, applicants mean a connection across which simple images, such as those of grids, that do not push the resolution limits of the image conveying apparatus, are not degraded beyond recognition. Applicants have invented an image preserving fiber optic cable connector that preserves images to the degree required for endoscopic surgery.
Applicants"" preferred connector functions by holding the tips of the fibers a certain small distance apart. It was unexpected that two fiber optic cables could be connected in this way. If the fibers were butted against one another, the image would suffer from fixed pattern noise, giving the image a mottled appearance and making it essentially useless. If the fibers were too far apart, the image would be blurred. Applicants unexpectedly discovered that there is a fiber tip spacing that allows the image to be transferred without noticeable fixed pattern noise, substantial loss of resolution, or excessive loss of image quality.
Applicants endoscopic surgical apparatus is expected to change the economics that affect the way endoscopic surgeries are performed. By placing the camera outside the sterile field, the expense and damage associated with sterilizing the camera can be avoided. By using a segmented fiber optic cable, the expenses associated with the cable itself can be kept under control. If the connection between the cable segments is made, according to applicants"" preferred embodiment, using a connector that functions by holding the ends of the cables a small distance apart, rather than by means of a lens, problems associated with connector itself will not present problems comparable to those that were associated with a camera within the sterile field.
Applicants"" invention is also expected to have a direct effect on the mechanics of endoscopic surgeries. The person conducting the procedure will no longer have to hold the camera, allowing greater control of the endoscope. In conjunction with other advances made by applicants, the invention is expected to contribute to the adoption of small diameter fiber optic endoscopes, which will mean less invasive surgeries, surgeries that can be performed on smaller joints, and surgeries that no longer have to be performed in a hospital.